Drill and throwaway insert

ABSTRACT

A drill improving the aligning accuracy of an insert and achieves a stable machining operation while maintaining the strength of the drill main body. The drill includes a drill main body rotatable about an axis, and a throwaway insert detachably attached to the drill main body. The drill main body includes a concave groove opening at a distal end face thereof, the concave groove includes guiding grooves extending in the direction of the axis on an inner surface thereof, the throwaway insert includes convex portions on an outer surface that are engageable with the guiding grooves, and the concave groove is formed so as to accommodate the throwaway insert. The throwaway insert is attached to the drill main body by insertion into the concave groove in a direction from the distal end face to the concave groove while engaging the convex portions with the guiding grooves.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. national phase application under 35 U.S.C. §371 ofInternational Patent Application No. PCT/JP02/12704 filed Dec. 4, 2002,and claims the benefit of Japanese Patent Application Nos. 2001-374324filed Dec. 7, 2001; 2002-227704 filed Aug. 5, 2002 and 2002-330575 filedNov. 14, 2002 which are incorporated by reference herein. TheInternational Application was published in Japanese on Jun. 12, 2003 asWO 03/047797 A1 under PCT Article 21(2).

TECHNICAL FIELD

The present invention relates to a drill having a throwaway insert(hereinafter referred to as an insert) which is detachably engageablewith grooves formed in a distal end face of a drill main body, andrelates to such an insert.

BACKGROUND ART

Conventionally, a drill is known in which a groove is formed on thedistal end face of the main body of the drill, an insert is attached tothe groove in a detachable manner, and the insert after having been usedis thrown away without resharpening, so that resharpening processes fortools are omitted, and the time for changing tools is reduced. Such atechnology in drills is disclosed, for example, in Japanese UnexaminedPatent Application, First Publication No. H11-197923. In the drilldisclosed in this document, an attachment hole having a circular holeshape is formed on a bottom face of a groove that is directed to adistal end, and an insert is provided with a cylindrical shank portionat a back face thereof that faces the bottom face. The insert isattached to the drill main body by inserting the shank portion into theattachment hole. The shank portion has a notch, and an engagementelement is provided inside the attachment hole; therefore, theengagement element engages the notch when the shank portion is insertedinto the attachment hole, and thus the insert is fixed to the drill mainbody.

In the above-mentioned drill, because the insert can be fixed to thedrill main body just by inserting the shank portion into the attachmenthole, the process of attaching the insert is simplified, and thusefficiency is obtained; however, a problem is encountered in that theshank portion may be broken if it is too thin since the connectionbetween the insert and the drill main body is achieved by the shankportion. Moreover, aligning (centering) of the insert with respect tothe drill main body is achieved only by the engagement of the shankportion with the attachment hole; therefore, the aligning accuracy maybe insufficient, which may lead to degradation in machining accuracy ofthe drill with respect to a workpiece.

In addition, when a workpiece is machined by a drill, in general,machining oil is supplied during the machining process. For this,conventionally, as shown in FIG. 11, a flow path 102 is formed in adrill main body 100 so as to extend in the direction of an axis O of thedrill main body 100, branched paths 103 are branched in two directionsfrom the flow path 102 at a distal portion thereof, the branched paths103 are connected to openings 104 which are formed in a distal end face107 of the drill main body 100, and machining oil is provided in amachining oil supply section 105 which is connected to the proximal endof the flow path 102 so that machining oil is supplied between theworkpiece and an insert 101 via the flow path 102, branched paths 103,and openings 104. However, because the branched paths 103 are formed inthe distal portion of the drill main body 100, the strength of thedistal portion, which is made thinner and weakened by a groove 106, isfurther decreased due to the branched paths 103; therefore, anotherproblem is encountered in that the distal portion of the drill main body100 may deform outwardly so as to be away from the groove 106, as shownin FIG. 12. Furthermore, the formation of the branched paths 103necessitates a greater number of manufacturing processes and morecomplicated manufacturing processes.

DISCLOSURE OF THE INVENTION

The present invention was conceived in view of the above circumstances,and objects thereof are to provide a drill which improves the aligningaccuracy between a drill main body thereof and an insert, and whichachieves a stable machining operation while maintaining the strength ofthe drill main body, and to provide an insert which is detachablyattached to such a drill.

In order to achieve the above objects, the present invention provides adrill including: a drill main body being rotatable about an axis; and athrowaway insert detachably attached to the drill main body, wherein thedrill main body includes a concave groove which opens at a distal endface thereof, the concave groove includes guiding grooves extending inthe direction of the axis on an inner surface thereof, the throwawayinsert includes convex portions on an outer surface thereof that areengageable with the guiding grooves, the concave groove is formed so asto accommodate the throwaway insert, and the throwaway insert isattached to the drill main body by being inserted into the concavegroove along a direction from the distal end face to the concave groovewhile engaging the convex portions with the guiding grooves.

According to the drill of the present invention, because the guidinggrooves extending in the direction of the axis are formed on the innersurface of the concave groove, the throwaway insert includes convexportions on the outer surface thereof that are engageable with theguiding grooves, and a serrated structure is constituted by the guidinggrooves and the convex portions, the insert can be easily attached tothe drill main body just by inserting the insert from the distal end ina sliding manner while engaging the convex portions with the guidinggrooves, and the aligning accuracy of the insert with respect to thedrill main body can be improved. In addition, because the serratedstructure is employed, the insert will not move with respect to thedrill main body when a workpiece is machined by the insert whilerotating the drill main body, and thus, the rotational force of thedrill main body is surely and efficiently transmitted to the insert.

In this case, it is preferable that the drill main body be provided witha flow path which extends from a bottom face of the concave groove thatfaces the distal end face, and which opens outside the drill main bodyso as to allow a predetermined fluid to flow therethrough, and a gap beformed between the guiding grooves and the convex portions engaging witheach other, which allows the fluid to flow between a distal end of thethrowaway insert and a proximal end thereof that faces the bottom faceof the concave groove. Accordingly, unlike in conventional practice, afluid can be stably supplied to the end of the insert without providinga flow path (branched paths) for machining oil (a fluid) in the distalend portion of the drill main body. Because a flow path is not formed inthe drill main body, the strength of the drill main body is maintained,a problem such as deformation can be avoided, and the manufacturingprocesses can be facilitated.

Even when gaps are provided, the attachment of the insert to the drillmain body is stabilized since the contact area between the insert andthe concave groove is ensured due to the serrated structure.

Moreover, in this case, it is more preferable that the bottom face beprovided with a cavity which is connected to the gap. Accordingly, thecavity can be used as a machining oil chamber, and the supply of themachining oil to the gap is stabilized. Furthermore, at least one ofridge portions of the convex portions and ridge portions between theguiding grooves may be chamfered so as to have a flat surface, whereby alarge cross section of the gap can be ensured, and a greater amount offluid such as machining oil can be supplied.

In addition, it is preferable that the convex portions be formed suchthat ridge portions thereof extend in the direction of the axis and arearranged side by side in the direction crossing the axis, and each ofthe convex portions is provided with a tapered portion that is inclinedtoward the direction of insertion. Accordingly, the aligning accuracy ofthe insert with respect to the drill main body can be improved, and theinsertion operation can be smoothly performed.

The present invention provides an insert that is insertable into aconcave groove formed at a distal end portion of a drill main body, theinsert including convex portions formed on an outer surface of thethrowaway insert such that ridgelines thereof extend in the direction ofinsertion, wherein the convex portions are arranged side by side, on theouter surface, in a direction crossing the direction of insertion.

According to the insert of the present invention, provided that guidinggrooves extending in the direction of insertion are formed on an innersurface of the concave groove formed in the drill main body, because theconvex portions are formed on the outer surface of the insert, aserrated structure is constituted by the guiding grooves and the convexportions; therefore, the insert can be easily attached to the drill mainbody just by inserting the insert from the distal end in a slidingmanner while engaging the convex portions with the guiding grooves, andthe aligning accuracy of the insert with respect to the drill main bodycan be improved.

In the insert of the present invention, it is preferable that each ofthe convex portions be provided with a tapered portion that is inclinedtoward the direction of insertion. Accordingly, the insertion operationinto the concave groove can be smoothly performed.

In addition, in the insert of the present invention, it is preferablethat the lengths of the tapered portions formed on the convex portions,when measured in the direction of insertion, be set to be different fromeach other. In this case, the lengths of the tapered portions may be setdepending on the shape of the distal end portion of the drill main body.Accordingly, the insertion operation can be smoothly performed since,when the insert is inserted into the concave groove of the drill mainbody, the convex portions can be respectively and simultaneously engagedwith the guiding grooves in the concave groove.

In this case, it is more preferable that the lengths of the taperedportions be set so as to be gradually decreased, in the directioncrossing the direction of insertion, from the center of the outersurface toward an end of the outer surface. More specifically, whereasthe shape of the concave groove at an insertion aperture thereof as seenfrom the side is normally configured to be a V-shape, the convexportions can be respectively and simultaneously engaged with the concavegroove by setting the lengths of the tapered portions so as to begradually decreased, in the direction crossing the direction ofinsertion, from the center of the outer surface toward the end of theouter surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are side views showing an embodiment of a drill of thepresent invention.

FIG. 2 is a diagram showing the drill in FIGS. 1A and 1B as viewed froma distal end side.

FIG. 3 is a cross-sectional view taken along the line A—A in FIG. 1B.

FIG. 4 is a side view of an insert.

FIG. 5 is a diagram showing the insert as viewed from a distal end side.

FIG. 6 is a side view of an insert.

FIG. 7 is a diagram for explaining a gap.

FIG. 8 is a diagram showing another embodiment of a drill of the presentinvention.

FIGS. 9A and 9B are diagrams showing another embodiment of an insert ofthe present invention.

FIGS. 10A, 10B, and 10C are diagrams for explaining an insertionoperation of the insert shown in FIGS. 9A and 9B into a concave grooveformed in a drill main body.

FIG. 11 is a diagram showing a conventional drill.

FIG. 12 is a diagram showing the problems of the conventional drill.

BEST MODE FOR CARRYING OUT THE INVENTION

A drill and an insert of the present invention will be described belowwith reference to the accompanying drawings. FIGS. 1A and 1B are sideviews showing an embodiment of a drill of the present invention, and inparticular, FIG. 1A is a side view as viewed in the Y-direction, andFIG. 1B is a side view as viewed in the X-direction. FIG. 2 is a diagramviewing FIG. 1A from a distal end side (the Z-direction side). FIG. 3 isa cross-sectional view taken along the line A—A in FIG. B. FIG. 4 is aside view of an insert as viewed in the Y-direction, FIG. 5 is a diagramviewing FIG. 4 from the distal end side, and FIG. 6 is a side view ofthe insert as viewed in the X-direction. Note that the X-direction isdefined as a diametric direction with respect to an axis O of a drill Din which a concave groove 6 to be explained below is formed, theY-direction is defined as a direction perpendicular to the X-directionand the axis O, and the Z-direction is defined as a direction parallelto the axis O, in which the positive (+) direction thereof is defined asthe direction from the distal end to the proximal end of the drill D.

In FIGS. 1A and 1B, the drill D includes a drill main body 1 beingrotatable about the axis O, and an insert 2 detachably attached to thedrill main body 1. The insert 2 includes cutting edge 2 a. The drillmain body 1 includes, at the proximal portion thereof, a shank portion 1a which is a large diameter portion. On the other hand, the drill mainbody 1 includes, at the distal portion thereof, a pair of chip dischargeflutes 4 which open at a distal end face 3 of the drill main body 1. Asshown in FIG. 2, the chip discharge flutes 4 are formed such that thechip discharge flutes 4 are opposite each other while having the axis Otherebetween, and extend toward the proximal end while being twistedabout the axis O in a direction opposite to the direction of drillrotation T during a drilling operation.

At the distal end portion of the drill main body 1, the concave groove 6is formed. The concave groove 6 opens at the distal end face 3 of drillmain body 1, and is formed so as to be concave toward the proximal endside, and so as to extend in a diametric direction with respect to theaxis O. More specifically, the concave groove 6 is formed such that aportion between the walls of the chip discharge flutes 4 at the distalend that face the direction of drill rotation T is cut out along avirtual plane including the axis O and along the diametric direction(X-direction). The concave groove 6 includes a bottom face 6 a whichfaces the distal end side and is perpendicular to the axis O, and a pairof inner faces 6 b parallel to each other, each of which isperpendicular to the bottom face 6 a and parallel to the axis O. Asshown in FIG. 1B, the concave groove 6 opens toward the distal end face3 in a rectangular shape as seen form the side. As shown in FIGS. 2 and3, the symmetrical center of the concave groove 6 coincides with theaxis O, and the concave groove 6 is formed so as to accommodate theinsert 2.

As shown in FIGS. 1A, 1B, and 2, on the inner faces 6 b of the concavegroove 6, there are formed guiding grooves 7 which extend in thedirection of the axis O. Each of the guiding grooves 7 includes pluralgrooves, which are arranged side by side in the direction crossing theaxis O, and each of which extends in the direction of the axis O. Theguiding grooves 7 are respectively formed on the inner faces 6 b. Theguiding grooves 7 are not formed on the entire surface of the innerfaces 6 b, and as shown in FIG. 2, each of the pair of guiding grooves 7is formed in a region of one of the pair of inner faces 6 b that facesthe direction of drill rotation T and includes the vicinity of the axisO so that the guiding grooves 7 are arranged at alternating locations inthe X-direction, and regions of the inner faces 6 b near the axis O,which are connected to a thinning portion of the distal end face 3, areformed so as to be flat. As shown in FIG. 7, the individual groovesincluded in the guiding grooves 7 and formed in a substantially V-shapeinclude concave arc portions at the bottom thereof. Ridge portionsformed between adjacent grooves are formed so as to have convex arcportions whose radius is made to be greater than that of the concave arcportions at the bottom.

As shown in FIGS. 1A and 1B, the drill main body 1 is provided with aflow path 5 that extends along the axis O. The flow path 5 is formed soas to connect a proximal end face 8 of the drill main body 1 and thebottom face 6 a of the concave groove 6. As shown in FIG. 1A, amachining oil supply unit 9, which is provided outside the drill mainbody 1 to supply machining oil (fluid) to the flow path 5, is connectedto a portion of the flow path 5 at the proximal end face 8 of the drillmain body 1. The machining oil supplied from the machining oil supplyunit 9, which is provided outside the drill main body 1, to the flowpath 5 is made to flow from a portion of the flow path 5 at the proximalend face 8 to the bottom face 6 a of the concave groove 6 that faces thedistal end side.

As shown in FIGS. 1B and 2, on the bottom face 6 a of the concave groove6, there are formed concave-shaped recesses 15 which may be formed by acounterboring process so as to be concave in the bottom face 6 a. Theinner end of each of the recesses 15 is connected to the distal end ofthe flow path 5. The recesses 15 respectively extend from the distal endof the flow path 5 to portions of the pair of inner faces 6 b of theconcave groove 6 where the guiding grooves 7 are formed, and furtherextend along the inner faces 6 a toward the outer periphery; however,the recesses 15 do not extend to the outer edges of the bottom face 6 a,i.e., the outer periphery of the drill main body 1 at the distal end,and stop within the bottom face 6. As shown in FIGS. 1B and 2, portionsof the recesses 15 that extend along the guiding grooves 7 on the innerface 6 b of the concave groove 6 are formed so as to be concave from theinner face 6 b in the direction opposite to the direction of drillrotation T. Due to the recess 15, a cavity 16 is formed between thedrill main body 1 and back face 2 c of the insert 2 when the insert isdisposed in the concave groove 6. The cavity 16 is used as a machiningoil chamber for retaining the machining oil supplied through the flowpath 5.

The insert 2 is disposed in the concave groove 6 such that the proximalend face 2 c thereof faces the bottom face 6 a. The insert 2 is made ofa hard material such as a cemented carbide, and is formed in asubstantially pentangular plate shape as shown in FIGS. 4, 5, and 6. Theinsert 2 is attached while being engaged with the concave groove 6. Theinsert 2 includes a through hole 10 that is formed at the center of theinsert 2 with respect to the X-direction so as to extend in thethickness direction (in the Y-direction). As shown in FIGS. 1A, 1B, and3, the through hole 10 is positioned so as to coincide with a mountinghole 11 when the insert is disposed in the concave groove 6, themounting hole 11 being formed at the center of the distal end portion ofthe drill main body with respect to the X-direction so as to extend inthe Y-direction and to open at the inner face 6 b of the concave groove6. The mounting hole 11 extends in the Y-direction from an outerperiphery of one (the upper portion with respect to the concave groovein FIG. 3) of the two sections of the distal end portion of the drillmain body which are formed by being divided by the concave groove 6while the diameter thereof is reduced in a tapered manner, i.e., via areduced diameter portion thereof, penetrates the one section, opens atthe inner face 6 b of the one section of the concave groove 6, furtherextends across the concave groove 6, and extends through the inner face6 b of the other section of the distal end portion of the drill mainbody 1 in the Y-direction, i.e., coaxially with a portion of themounting hole 11 in the one section. The mounting hole 11 is formed as astopped hole which does not penetrate through the drill main body 1, anda female thread is formed therein. By disposing the insert 2 in theconcave groove 6 by inserting a bolt as a fixing element 12 from the onesection into the mounting hole 11 and the through hole 10, and byscrewing the bolt into the female thread, the insert 2 is fixed andconnected to the drill main body 1 while the countersunk-head of thebolt as the fixing element 12 firmly contacts the reduced diameterportion, as shown in FIG. 3. The through hole 10 and the mounting hole11 are disposed at the center with respect to the X-direction, andextend in the direction perpendicular to the axis O for the case of thefixing element (bolt) 12 that is inserted into and engaged with thethrough hole 10 and the mounting hole 11.

As shown in FIGS. 4 and 5, on the outer surfaces 2 b of the insert 2,there are formed convex portions 13 which are engageable with theguiding grooves 7 of the drill main body 1. The convex portions 13extend in the direction of the axis O, i.e., the ridgelines thereofextend in the direction of the axis O, and are arranged side by side inthe direction crossing the axis O. The convex portions 13 are formed inregions which correspond to the portions of the concave groove 6 inwhich the guiding grooves 7 are formed in a state in which the insert 2is disposed in the concave groove 6. More specifically, the convexportions 13 are respectively formed on the outer surfaces 2 b of theinsert 2, and the convex portions 13 are formed in the regions of thepair of outer surfaces 2 b that face the direction opposite to thedirection of drill rotation T and include the vicinity of the axis O sothat the convex portions 13 are arranged at two alternating locations inthe X-direction. The regions of the outer surfaces 2 b of the insert 2corresponding to the inner faces 6 b which are formed to be flat, andwhich are connected to the thinning portion, are formed to be flat so asto make a surface contact with the flat portions of the concave groove6. As shown in FIG. 7, in cross-sectional view taken along a planeperpendicular to the axis O, the ridge portions of the convex portions13 formed in a substantially V-shape include convex arc portions. Valleyportions formed between adjacent convex portions 13 are formed so as tohave concave arc portions whose radii are made to be less than those ofthe convex arc portions, and the included angle of the V-shape of theconvex portions 13 is the same as the included angle of the V-shape ofthe grooves of the guiding grooves 7

Moreover, as shown in FIG. 7, in a state in which the insert 2 isdisposed in the concave groove 6 while the convex portions 13 areengaged with the guiding grooves 7, gaps 14 are formed between theconvex portions 13 formed on the insert 2 and the guiding grooves 7formed on the concave groove 6 of the drill main body 1, and at theapexes and valleys of the convex portions 13. More specifically, theradii of the convex arcs of the ridge portions of the convex portions 13are set to be greater than those of the concave arcs of the grooves ofthe guiding grooves 7, and the radii of the concave arcs of the bottomsbetween the adjacent convex portions 13 are set to be less than those ofthe convex arcs of the ridge portions between the adjacent grooves ofthe guiding grooves 7. By engaging the convex portions 13 with theguiding grooves 7 so that the walls of the grooves in the guidinggrooves 7 and side surfaces of the convex portions 13 having the sameincluded angle of the V-shape as that of the guiding grooves 7 make asurface contact therebetween, the gaps 14 are formed between the ridgeportions of the convex portions 13 and the bottom portions of thegrooves in the guiding grooves 7, and between the valleys between theadjacent convex portions 13 and the ridge portions between the adjacentgrooves in the guiding grooves 7. The size of the gaps 14 is determinedso that machining oil is allowed to flow therethrough, i.e., machiningoil is allowed to flow between the distal portion of the insert 2 andthe proximal portion thereof, and thus, when the insert 2 is disposed inthe concave groove 6, the machining oil, which is supplied to the bottomface 6 a of the concave groove 6 via the flow path 5, is allowed to flowthrough the gaps 14. More specifically, the machining oil, which issupplied to the concave groove 6 via the flow path 5, is allowed to flowout at the distal portion of the insert 2.

In addition, the cavity 16 is formed in a portion of the bottom face 6 aof the concave groove 6 which corresponds to the connection regionbetween the guiding grooves 7 and the convex portions 13. Morespecifically, portions of the recesses 15 forming the cavity 16 thatextend along the guiding grooves 7 in the inner faces 6 b of the concavegroove 6 are formed so as to be concave from the inner faces 6 b in thedirection opposite to the direction of drill rotation T. Accordingly,when the insert 2 is disposed in the concave groove 6, the cavity 16 isconnected, over the region where the cavity 16 is formed, to the gaps 14which are formed between the convex portions 13 and the grooves of theguiding grooves 7.

When the insert 2 is disposed in the concave groove 6, the distal endface of the insert 2 is formed in an isosceles triangular shape(V-shape), i.e., the distal end face of the insert 2 is formed so as toextend toward the proximal end side as it extends outward. The cuttingedges 2 a are respectively formed on the intersecting ridges between thedistal end face and the rake faces 20, of the outer surfaces 2 b of theinsert 2, which face the direction of drill rotation T in a state inwhich the insert 2 is attached to the drill main body 1. The rake face20 becomes narrower and is inclined toward the opposite outer surface 2b as it extends toward the proximal end of the insert 2, and isconnected to the wall that faces the direction of drill rotation T inthe mounted state. The convex portions 13 are formed on the outersurfaces 2 b where the rake faces 20 are not formed. The back face 2 cof the insert 2 extends in the direction perpendicular to the axis O ina state in which the insert 2 is attached to the drill main body 1, andmakes a surface contact with the bottom face 6 a of the concave groove 6where the recesses 15 are not formed.

Next, regarding the drill D having the structure explained above, theoperation for attaching the insert 2 to the drill main body 1 and thedrilling operation will be explained below.

When the insert 2 is to be attached to the drill main body 1, the insert2 is oriented so that the extending direction of the through hole 10 ofthe insert 2 coincides with the extending direction of the mounting hole11 of the drill main body 1, and then the insert 2 is inserted into theconcave groove 6 from the side of the distal end face 3 (from the openside) in the +Z direction, i.e., in the insertion direction S, which isthe direction of the axis O toward the proximal end (refer to FIG. 11A).When the insert 2 is inserted into the concave groove 6, the insert 2 isinserted in a sliding manner while engaging the convex portions 13 onthe outer surfaces 2 b of the insert 2 with the guiding grooves 7 on theinner surfaces 6 b of the concave groove 6. By inserting the insert 2,the back face 2 c of the insert 2 makes a surface contact with thebottom face 6 a of the concave groove 6. Because the position at whichthe back face 2 c of the insert 2 contacts the bottom face 6 a of theconcave groove 6 is determined such that the through hole 10 of theinsert 2 coincides with the mounting hole 11 of the drill main body 1,at this stage, the fixing element 12 can be inserted into the throughhole 10 and the mounting hole 11, and the insert 2 can be connected andfixed to the drill main body 1 by screwing the fixing element 12 such asa bolt into the mounting hole 11 having the female thread.

The thickness of the insert 2 where the rake faces 20 are formed is setto be less than the thickness of the insert 2 where the convex portions13 are formed (i.e., the thickness at the apexes of the convex portions13). Accordingly, the insertion operation is not hindered when theinsert 2 is inserted into the concave groove 6 while making the convexportions 13 slide with respect to the guiding grooves 7.

When the insert 2 is to be detached from the drill main body 1, thefixing element 12 is unscrewed from the mounting hole 11 and removedtherefrom, and the insert 2 is removed from the concave groove 6 so thatthe insert 2 is separated from the drill main body 1.

After fixing the insert 2 to the drill main body 1, a drilling operationis applied to a workpiece while supplying machining oil from themachining oil supply unit 9 to the flow path 5 of the drill main body 1.The machining oil supplied to the flow path 5 is supplied from the endof the flow path 5 to the cavity 16 acting as a machining oil chamber.Because the cavity 16 is connected to the gaps 14, the machining oil isallowed to flow out at the distal end of the insert 2 via the gaps 14.Accordingly, the drilling operation can be performed while supplyingmachining oil to the workpiece.

As explained above, because the guiding grooves 7 that extend in thedirection of the axis O are provided on the inner surfaces 6 b of theconcave groove 6, the convex portions 13 that are engageable with theguiding grooves 7 are provided on the outer surfaces 2 b of the insert2, and a serrated structure is constituted by the guiding grooves 7 andthe convex portions 13, the insert 2 can be easily attached to the drillmain body 1 just by inserting the insert 2 while engaging the convexportions 13 with the guiding grooves 7. Moreover, the aligning accuracyof the insert 2 with respect to the drill main body 1 can be improved.Furthermore, because the insert 2 is tightened by the fixing element 12(bolt) such that the concave groove 6 is made narrower, and the insert 2is pressed from the Y-direction to the direction slightly inclined withrespect to the direction connecting the pair of inner surfaces 6 b and 6b of the concave groove 6 in which the guiding grooves 7 are formed, theconvex portions 13 can be further reliably engaged with the guidinggrooves 7, and the aligning accuracy can be further improved. Inaddition, by employing a serrated structure, the insert 2 will not movewith respect to the drill main body 1 when a workpiece is machined bythe insert 2 while rotating the drill main body 1, and thus, therotational force of the drill main body 1 is surely and efficientlytransmitted to the insert 2. Accordingly, the machining process isstabilized, and high machining accuracy can be achieved.

Moreover, because the flow path 5, which connects the bottom face 6 a ofthe concave groove 6 that faces the distal end side to the outside ofthe drill main body 1, is formed in the drill main body 1, and the drillmain body 1 and the insert 2 are formed so that the gaps 14 are formedbetween the guiding grooves 7 and the convex portions 13 in the engagedstate, the machining oil supplied from the flow path 5 is allowed toflow out at the distal end of the insert 2 via the gaps 14; therefore,the machining oil can be stably supplied to the distal end of the insert2 without forming the branched paths for supplying machining oil in thedistal end portion of the drill main body, as shown in FIG. 11. Becausea flow path is not formed in the distal end portion of the drill mainbody 1, the strength of the drill main body 1 is maintained, a problemsuch as deformation can be avoided, and the manufacturing processes ofthe drill main body 1 can be facilitated.

Furthermore, because, in the engaged state, the insert 2 contacts thedrill main body 1 in such a manner that the gaps 14 are formed at onlylocations corresponding to the apexes (ridgelines) of the convexportions 13 (i.e., locations corresponding to the valleys (groovebottoms) of the guiding grooves 7) and the valleys between the convexportions 13 adjacent to each other (i.e., locations corresponding toridgelines of the adjacent grooves of the guiding grooves 7), and theside surfaces of the convex portions 13 make a surface contact with thewalls of the guiding grooves 7 at other locations, the contact areabetween the insert 2 and the drill main body 1 is sufficiently ensured,and the insert 2 can be stably attached to the drill main body 1.

Moreover, because the cavity 16, acting as a machining oil chamber, isprovided in the bottom face 6 a of the concave groove 6 so as to beconnected to the gaps 14, machining oil can be stably supplied to thegaps 14, and thus the supply of machining oil to the distal end of theinsert 2 during a machining process is ensured.

In the above description of this embodiment, machining oil is suppliedto the distal end of the insert 2 via the gaps 14 formed between theinsert 2 and the drill main body 1; however, as shown in FIG. 8,branched paths 103, which are branched from the flow path 5 and areconnected to openings 104 at the distal end face 3 of the drill mainbody 1, may be formed. In other words, the branched paths shown in FIG.11 and the gaps 14 according to the present invention may besimultaneously employed. Moreover, the openings 104 of the branchedpaths 103 may be formed in the outer peripheral surface of the distalend portion of the drill main body 1. In this case, it is preferablethat the total cross-sectional area of the gaps 14 be less than that ofthe branched paths 103, so that machining oil can be supplied throughthe gaps 14, which open at the vicinity of the cutting edges 2 a, athigher pressure. On the other hand, the strength of the distal endportion of the drill main body 1 is ensured since the branched paths 103are not provided. The gaps 14 may be formed at only one of the ridgeportions of the convex portions 13 (i.e., the groove bottoms of theguiding grooves 7) and the valleys between the convex portions 13adjacent to each other (i.e., the ridgelines of the adjacent grooves ofthe guiding grooves 7). Furthermore, when dry cutting is performed on aworkpiece, compressed air acting as a fluid may be supplied instead ofsupplying machining oil from the machining oil supply unit 9.

Next, another embodiment of the insert according to the presentinvention will be explained. The same reference symbols are applied tothe same or equivalent elements in the above embodiment, andexplanations thereof are simplified or omitted.

FIG. 9A is a side view showing an insert of this embodiment, and FIG. 9Bis an enlarged perspective view showing the main part.

As shown in FIG. 9A, the insert 2 is formed in a substantiallypentangular plate shape, and is to be inserted into the concave groove 6of the drill main body 1. On the outer surfaces 2 b of the insert 2,there are formed convex portions 13 which are engageable with theguiding grooves 7 of the drill main body 1. The convex portions 13 areformed so as to extend in the direction of insertion into the concavegroove 6 (i.e., in the direction of axis O or in the Z-direction), i.e.,the ridgelines thereof coincide with the direction of insertion. Theconvex portions 13 are arranged side by side in the direction crossingthe direction of insertion (i.e., in the X-direction). The convexportions 13 are formed at locations corresponding to the guiding grooves7 of the concave groove 6 in a state in which the insert 2 is disposedin the concave groove 6.

The convex portions 13 are respectively provided with tapered portions30 (30A to 30D) each of which is inclined toward the proximal end face 2c of the insert 2. In other words, the tapered portions 30 are formed insuch a manner that the thickness of the insert 2 becomes less (i.e., theheight of the convex portions 13 is gradually decreased) as it extendstoward the proximal end face 2 c of the insert 2.

The lengths of the tapered portions 30A to 30D formed on the convexportions 13, when measured in the direction of insertion, i.e., thelengths La to Ld of the tapered portions 30A to 30D measured in theZ-direction, are set so as to be different from each other. In thisembodiment, as shown in FIG. 9B, the lengths La to Ld of the taperedportions 30A to 30D are set so as to be gradually decreased, in thedirection crossing the direction of insertion, from the center of theouter surface 2 b with respect to the X-direction toward an end of theouter surface 2 b. More specifically, the length Ld of the taperedportion 30D at the center of the outer surface 2 b with respect to theX-direction is the greatest, and the lengths Lc, Lb, and La are set soas to be gradually decreased toward the end of the outer surface 2 bwith respect to the X-direction. In addition, angles θa to θd betweenthe lines parallel to the Z-axis (axis O) and the surfaces of thetapered portions 30A to 30D are set such that the angle θd correspondingto the tapered portion 30D at the center with respect to the X-directionis the smallest, and the angles θc, θb, and θa of the tapered portions30 are set so as to be gradually increased toward the end of the outersurface 2 b with respect to the X-direction.

The tip sides (−Z sides) of the tapered portions 30A to 30D are arrangedon a straight line M, and the angle between the line M and the X-axis isset to be θM (refer to FIG. 9A). The back ends of the tapered portions30A to 30D coincide with the proximal end face 2 c of the insert 2,which is perpendicular to the axis O. Accordingly, the line M isinclined toward the proximal end face 2 c as it extends from the centerwith respect to the X-direction toward the end of insert 2, as shown inFIG. 9A. The tapered portions 30A to 30D are formed such that the backends of the convex portions 13 are chamfered by a single plane includingthe line M.

On the other hand, as shown in FIG. 10A, the distal end portion of thedrill main body 1 is formed in a substantially V-shape as seen from theside, and the angle between the distal end face 3 and the X-axis issubstantially equal to the angle θM between the line M and the X-axis.In other words, the lengths La to Ld of the tapered portions 30A to 30Dare set so that the line M, which is defined by the tapered portions 30Ato 30D, substantially coincides with the inclination (shape) of thedistal end face 3.

Next, the operation for attaching the insert 2 having the structureexplained above to the concave groove 6 of the drill main body 1 will beexplained below with reference to FIGS. 10A, 10B, and 10C.

As shown in FIG. 10A, first, the proximal end face 2 c of the insert 2is disposed so as to be opposite the concave groove 6. As explainedabove, the angle between the distal end face 3 and the X-axis is set tobe substantially equal to the angle θM between the line M and theX-axis.

Then, the insert 2 is inserted into the concave groove 6. As shown inFIG. 10B, during the insertion of the insert 2 into the concave groove6, because the angle between the distal end face 3 and the X-axis is setto be substantially equal to the angle θM between the line M and theX-axis, the convex portions 13 formed on the insert 2 respectively andsimultaneously engage the guiding grooves 7 formed in the concave groove6. More specifically, because the convex portions 13 simultaneouslyengage the guiding grooves 7 during the inserting operation, theinserting operation of the insert 2 can be smoothly and steadilyperformed. Then, the insert 2 is further inserted so as to be disposedin the concave groove 6 as shown in FIG. 10C.

In this embodiment, because the lengths La to Ld of the tapered portions30A to 30D are set so that the line M substantially coincides with theinclination (shape) of the distal end face 3, the convex portions 13respectively and simultaneously engage the guiding grooves 7 formed inthe concave groove 6 during the inserting operation. When the distal endface 3 is formed not in a V-shape, but in a W-shape, or when theportions of the insert 2 at the ends with respect to the X-direction areprojected in the −Z-direction from the center portion thereof, thelengths La to Ld of the tapered portions 30A to 30D are set depending onthe shape of the distal end face 3 so that the convex portions 13respectively and simultaneously engage the guiding grooves 7 formed inthe concave groove 6. For example, when the distal end face 3 is formedin a W-shape, the line (line M) defined by connecting the tip ends (endsat −Z side) of the tapered portions 30A to 30D is also set in a W-shape.

In this embodiment, a through groove 31, which has a U-shaped crosssection while opening at the proximal end face 2 c, and which penetratesthrough the insert 2 between the outer surfaces 2 b, is provided at thecenter of the insert 2 with respect to the X-direction, instead of thethrough hole 10 of the insert 2. Due to the through groove 31, when theinsert 2 is to be removed, the insert 2 can be removed withoutcompletely removing the fixing element (bolt) 12 from the drill mainbody 1. Furthermore, in this embodiment, the ridge portions of theconvex portions 13 are chamfered by a plane that extends parallel to theouter surfaces 2 b, i.e., a plane perpendicular to the Y-axis.Accordingly, the cross-sectional area of the gaps 14 formed between theridge portions and the groove bottoms of the guiding grooves 7 can beincreased, so that a greater amount of predetermined fluid such asmachining oil can be supplied to the distal end portion of the drillmain body 1, while maintaining the stable attachment of the insert 2. Inthe guiding grooves 7, the ridge portions between the grooves adjacentto each other may be similarly chamfered, so that both the ridgeportions of the convex portions 13 and the ridge portions between thegrooves of the guiding grooves 7 are chamfered by planes.

INDUSTRIAL APPLICABILITY

According to the present invention, because the guiding groovesextending in the direction of the axis are formed on the inner surfaceof the concave groove, the throwaway insert includes convex portions onthe outer surface thereof that are engageable with the guiding grooves,and a serrated structure is constituted by the guiding grooves and theconvex portions, the insert can be easily attached to the drill mainbody just by inserting the insert from the distal end in a slidingmanner while engaging the convex portions with the guiding grooves, andthe aligning accuracy of the insert with respect to the drill main bodycan be improved. In addition, because the serrated structure isemployed, the insert will not move with respect to the drill main bodywhen a workpiece is machined by the insert while rotating the drill mainbody, and thus, the rotational force of the drill main body is surelyand efficiently transmitted to the insert. In addition, by providingtapered portions on the convex portions of the insert, the insertionoperation into the concave groove of the drill main body can be smoothlyperformed. Accordingly, a stable drilling operation can be performedwhile maintaining preferable machining accuracy.

1. A drill having an axis comprising: a drill main body being rotatableabout the axis including: a distal end face formed in an isoscelestriangle shape; a concave groove which opens to the distal end face andforms a plate-shape space along the axis; and a plurality of guidinggrooves provided on an inner surface of the concave groove, andextending in a direction of the axis; and a throwaway insert formed in aplate-shape and detachably attached to the plate-shape space of thedrill main body including: a plurality of convex portions provided on anouter surface of the throwaway insert, which are formed such that eachof ridges thereof extends in the direction of the axis, arranged side byside in a direction crossing the axis, and engageable with the guidinggrooves; and tapered portions, each of which is connected to eachproximal end of the convex portions, and inclined so that a heightthereof with respect to an outer surface of the throwaway insert islowered toward a proximal end of the throwaway insert along thedirection of the axis, wherein distal ends of the guiding grooves andthe tapered portions are arranged following the isosceles triangle shapeof the distal end face of the drill main body, and the throwaway insertis attached to the drill main body by being inserted into the concavegroove along the axis from the distal end face to the concave groovewhile engaging the convex portions with the guiding grooves.
 2. A drillaccording to claim 1, wherein the drill main body is provided with aflow path which extends from a bottom face of the concave groove thatfaces toward the distal end face, and which opens outside the drill mainbody so as to allow a predetermined fluid to flow therethrough, and gapsare formed between the guiding grooves and the convex portions engagingwith each other, which allow the fluid to flow between a distal end ofthe throwaway insert and the proximal end thereof that faces the bottomface of the concave groove.
 3. A drill according to claim 2, wherein thebottom face is provided with a cavity which is connected to the gaps. 4.A drill according to claim 2, wherein at least ridge portions of theconvex portions ridge portions or between the guiding grooves arechamfered so as to have flat surfaces.
 5. A drill according to claim 1,wherein lengths of the tapered portions are set so as to be graduallydecreased, in a direction crossing a direction of insertion, from acenter toward an end of the outer surface.